Welcome to the Science of Sport where we bring you the second, third, and fourth level of analysis you will not find anywhere else.

Be it doping in sport, hot topics like Caster Semenya or Oscar Pistorius, or the dehydration myth, we try to translate the science behind sports and sports performance. Consider a donation if you like what you see here!

Today we forge ahead with the Q & A I did earlier this year with Run 2 Day magazine, which I’ve cut into segments to make up a series while I’m travelling.

Yesterday, I posted twice, dealing collectively with some the questions around barefoot running and running shoes, the mechanical changes they cause, and some of the possible physiological consequences of these changes. Clearly, there is a lot more to be said than even what I did, but I’m moving on with Part 3 today, and looking at some of the shoe research out there. After the information overload yesterday, I’m going with only two questions today – 8 and 9 in the series, looking at some of the questions around shoes in particular. Enjoy!

8. Is there any evidence that either (shoe or barefoot) is better in terms of both performance and injury prevention?

No conclusive evidence, as I’ve mentioned in the previous posts. There is however some circumstantial evidence for both sides – the shoe industry didn’t grow into a billion dollar one based on rumor only – there is some science behind it. It’s just that it’s pretty weak, failing to show that the prescription of certain shoes to certain individuals actually does anything to prevent injury (Richards et al, 2009[cite source=pubmed]18424485[/cite]), and failing to show that the shoes contributed to the injury in the first place.

A study published in 2007 attempted to pull together all the research on running injuries (van Gent et al, 2007[cite source=pubmed]17473005[/cite]), and a few things were pretty clear. First, there were very few good, scientifically sound studies investigating running injuries and their cause. Incredibly, given that running is the most studied sport, and that the prevalence of injury is up above 60%, only 17 studies were deemed of sufficient standard to be included in the review. It’s quite amazing. The only thing that study really concluded was that training volume was highly predictive of injury.

On the other side of the table is a growing body of circumstantial evidence for why shoes may not work. For example, the loading forces are not different in new and old shoes, because runners change their kinematic patterns (Kong et al. 2009[cite source=pubmed]18801775[/cite]). The table below shows the measured changes in the study. I apologize for not redrawing it for you, but time is tight. I’ve highlighted the main finding, which is that the maximum vertical force (Fmax) and the maximum loading rate (Gmax) are not different in worn shoes (200 miles of running). The study also found that there is less forward lean and more plantar flexion in worn shoes, and that stance time was greater in worn shoes.

What the study didn’t measure was muscle activation, which is something I discuss in Question 10 (tomorrow, probably), because that would likely have been different too, as the runners adjust their muscle activity to maintain constant tissue impacts – this is called muscle tuning, a concept that is really important in how we understand the body’s cushioning ability.

The eventual conclusion of the Kong et al study was that runners should choose shoes based on properties other than cushioning, because the body will find the ideal cushioning anyway. This doesn’t suggest that the gadgets designed to prevent injury through cushioning would be that effective (or, of course, that shoes wear out, if you wish to adopt that position!).

Another study found that runners who ran in the most expensive shoes were just as likely to get injured as those who ran in the cheap shoes, lacking all the protective gadgets and functions (Clinghan et al, 2008[cite source=pubmed]17932096[/cite]). Here, there is the counter-argument that the runner who buys the very expensive shoe might be more injury-prone to begin with – perhaps they buy the shoe because they have a history of injuries, whereas those who settle for the cheap shoe do so because they’ve never been on the receiving end of running injuries (the study did control for running volume, by the way, in case you’re sharp enough to be wondering if the cheap shoe buyers ran less).

We also know that the shape of the foot is altered by wearing shoes, and so is its function (D’Aout et al, 2009[cite]10.1080/19424280903386411[/cite]). This study was brought to my attention yesterday, and it’s interesting because it shows that the “natural” shape and function of the foot changes with chronic shoe-wearing, which provides something of an explanation for why it’s so difficult to go from years of wearing shoes to running barefoot.

And then most recently, it’s been found that if you prescribe shoes to runners based on the shape of the foot and arch (as is typically done, because people who pronate are supposed to have flat feet – this is often called the “wet test”, where you have to look at the wet footprint left behind to tell you whether you need a motion control shoe or a cushioned, neutral shoe) there’s no difference in injury rates. Even controlling for physical fitness and age, you do no better at reducing injury rates than if you just give every runner the same shoe (Knapik et al. 2010[cite source=pubmed]20117594[/cite]).

So the idea that you have to prescribe certain shoes to certain runners, because the shoe is going to help prevent injuries is not borne out by research. That’s not the same thing as saying shoes are unnecessary, mind you, but it does challenge the conventional wisdom. And this is a movement that is gaining momentum all the time.

So currently, there’s little conclusive evidence. Both sides are poking holes in the other’s arguments, pointing out the lack of evidence, but we still await a definitive answer, one that will only really come when a long-term, prospective study is done. As I said, it’s incredibly difficult to find, because injuries are so complex and difficult to predict, and the study to answer this question may be hypothetical only.

9. If there is evidence for the opposite, why does everyone – including manufacturers – believe that shoes prevent injury?

Well, for the manufacturers, the answer is obvious – they have a strong incentive to believe their product is not only effective but indispensible. For everyone else, thirty years of investing, marketing and belief, is the simple answer. The shoe industry grew rapidly in about the 1970s, co-inciding with the huge running boom of the time. Until that point, shoes were really minimalist. If you ever have the opportunity to look at the shoes that runners used prior to about 1970, you’ll be amazed at how basic they were. In fact, they resembled the modern day lightweight shoe. No gel pads, air cushions, torsion devices, and certainly no built up heel.

The explosion that accompanied the running boom saw massive financial incentives created, and I don’t think it’s oversimplifying things to say that a market was suddenly created, that this market had a need for a product, and it was lucrative. Then, I’m sure a good number of people with good intentions started to theorize about how they could help reduce injuries, and the concept was born. Once it became conventional wisdom, it was difficult to reverse, just as most things are, I guess. The pervasive message has always been that shoes are vital. It’s not difficult to get this message out, because you have to remember that a runner only really thinks about one piece of equipment, which is also his “interface” with the road.

However, and this is the side that none of the barefoot advocates wish to hear, part of the reason we believe shoes help prevent injury is that it’s possible that shoes DO prevent injury, or at the very least enable people to start running! I’ve spoken about the lack of evidence for either position, but there’s good reason to believe that some people’s shoes really do help them run, or run more than they would be able to in those light shoes.

Take a 100kg (220 lbs) man who wants to take up running. Remember, prior to 1970, he would never consider running a marathon. Today, he can, which is a great plus for our sport. However, he may be coming to running from 20 years of inactivity, with weakened supporting muscles, he’s heavy. He may be doomed if he could not get a shoe that provided some support and cushioning, purely because the first few weeks would be so uncomfortable, even in a minimalist shoe, that he may really struggle. Perhaps one day, with enough training, he’d succeed in light shoes (or barefoot), but you would have to work very hard to convince me that this person would ever get off the ground without more supportive shoes. This man, straight into a lightweight pair of shoes, would not be a runner, I have no doubt about this, and so it would be false to say that shoes don’t help at least some of the time.

Next up: Shoe-cushioning, muscle-tuning and intelligent muscles

That’s it for now – I know it’s probably frustrating when posts end “in the middle of nowhere”, but hopefully you can forgive the lack of smooth continuity in favour of shorter, manageable posts. I don’t think I’ve yet figured out how to do these long series!

Next up, I answer a few questions on the cushioning properties of the muscles, as opposed to shoes, and how the body “senses” the ground. But that’s for tomorrow, so join us then!

Did you know?

We published The Runner's Body in May 2009. With an average 4.4/5 stars on Amazon.com, it has been receiving positive reviews from runners and non-runners alike. Available for the Kindle and also in paperback.